Thiel's CS 3.6 speakers have been praised highly in print--just call for Thiel's marketing packet to read and behold. I own a pair and love their lack of coloration (except for a bit of purr in the bass) and unmatched ability to resolve whatever signal you throw at them. They simply sound more lifelike than any other speaker I've heard in my system, and if they were made by a more obscure company, they surely would cost much more than their $3900 a pair. But the Thiels are not perfect--we all know that no component is. Their impedance is low, between 2 and 4 ohms, solid state territory--or so it goes. There is something redeeming about that brutal load, however. It's fairly constant with frequency, with relatively little variation across the spectrum. This means that the greater peaks and valleys of other speakers' impedances, those that can give tube amps (with their normally highish output impedance) fits, are less of a going concern with the Thiels. The Thiels' overall loudness may be affected, but only when they're driven by the most underpowered of amps.
I've used my Thiels with a variety of tube amps, including a conrad-johnson Premier 11A (70 watts, ultra fidele), a pair of Lumley monoblocks (ssssmoooth) and a Mesa Baron--which drove them the best so far. It may be trite to say, but the Baron fleshes out the music; it's powerful (even in the bass), dynamic and very liquid. I'm also awaiting arrival of a pair of Quicksilver M135 monoblocks. These, with their big power supplies and muscle into low-impedance loads, should be the best yet. If only the Quicksilvers, hard-wired as they are, didn't take such a darn long time to get here.
What the Thiels don't have is snob appeal. You won't be the first on your block--or in your hemisphere--to hear the word. Dealers often ridicule the Thiels--those dealers who don't sell them. They always have something much better, and if what they have costs more--well, you want the best, don't you?
Don't fall for it. I've listened to many of the more elite, and expensive, speakers and none of them do it for me the way the Thiels do. Their execution is top-shelf, and given the Thiels' incredible transparency and resolution, and their low coloration, I'd say they're a bargain to boot.